This invention relates to an expansive demolition agent to be used for demolishing brittle materials such as boulders, bedrocks or concrete.
Heretofore, a method for demolishing brittle materials such as boulders, bedrocks or concrete has been known, in which a hole is drilled in a brittle material, and the hole is poured with a slurry prepared by mixing a powdered expansive demolition agent and water, to demolish the brittle material utilizing an expansive pressure generated by the hydration of the powdered expansive demolition agent. The powdered expansive demolition agent used has been prepared by pulverizing a clinker for manufacturing the powdered expansive demolition agent to Blaine specific surface areas of 2,000 to 2,500 cm.sup.2 /g. The resulting powdered expansive demolition agent is previously mixed with water to obtain a slurry, which is used to pour into the hole drilled in the brittle material. However, this method has the following problems.
(1) The powdered expansive demolition agent must be weighed and mixed immediately prior to applying the slurry, thus requiring a complex work.
(2) If the slurry of the powdered expansive demolition agent is kept standing as it is, the hydration reaction proceeds to generate dangerous heat.
(3) For a large hole diameter or at a high working temperature, the hydration heat generated by the hydration reaction accumulates within the hole to produce water vapor from the component water in the slurry, and the slurry can dangerously be blown out of the hole opening by the vapor pressure.
(4) When the brittle body to be demolished is in a river or sea, or if the hole is filled with water due to water spring in the hole or rainfall after drilling the hole, the slurry in the hole is diluted with water and an effective expansive pressure cannot be developed. Then, a bag such as of polyethylene must be previously inserted in the hole, and the slurry must be poured into the bag, thus requiring a further complex work. Even by the method, underwater or undersea demolishing is difficult.
(5) Demolishing a brittle material using the slurry based on the powdered expansive demolition agent, mixed with water, requires a period of 10 to 20 hours because its reaction time is adjusted in view of safety. Thus, it requires a longer time than other demolishing methods using explosives or heavy machines. This results in an increased working period or a waiting time of workers, thus leading to inferior economy.
(6) If, in order to shorten the demolition time, a hydration accelerator such as calcium chloride is added to the powdered expansive demolition agent, or the particle size of the powdered expansive demolition agent is further decreased, the hydration reaction is excessively accelerated to accumulate the hydration heat, which tends to blow out the slurry, thus further increasing danger.
To eliminate such disadvantages, the powdered expansive demolition agent has been pressure-molded by a bricket machine or a roll press, and further processed into particles within a certain range of particle size to produce a pressure-molded powdered expansive demolition agent. The pressure-molded powdered expansive demolition agent has been used to pour into the hole, and water has been poured into the hole to demolish it.
The above described pressure-molded powdered expansive demolition agent, however, has the following problems when used for demolishing brittle materials.
(1) Since the pressure-molded powdered expansive demolition agent is prepared by molding under pressure, and then adjusting its particle size within a certain range by a granulating machine, it requires a complicated production process and is high in cost.
(2) Since there is a limit in the molding pressure and the resulting particles have a limited strength, it tends to break into fine powder during transportation and storage.
(3) With an increased content of fine powder, water penetration into the powdered demolition agent after pouring into the hole is disturbed, and water will not penetrate over the entire agent, or when pouring into a hole which is previously poured with water, the fine powder will be concentrated in the upper layer of the agent, resulting in uneven pouring and uneven development of expansive pressure.
(4) An increased content of fine powder reduces voids between particles, which makes water vapor generated by the hydration heat difficult to flow out, thereby causing danger of blowing-out.
(5) The pressure-molded powdered expansive demolition agent is easily broken when contacting with water, which pours into initially existing voids between particles and makes water vapor difficult to flow out, thereby causing danger of blowing-out.
(6) There is a method, to prevent blowing-out of the agent, in which the amount of water added is decreased to below a certain level to reduce contact of water with the powdered demolition agent in order to leave the voids unfilled. However, this results in incomplete hydration of the powdered demolition agent due to an insufficient amount of water, and hence, an expansive pressure necessary for demolishing cannot be obtained.